[sdiy] Leaving off a pot?

[Harry Bissell Jr]

My point was not "don't try it"...

it was "don't use protection circuits as
design elements for normal use"

If you NEED to limit current... see to it that
the load cannot draw more current than you intend...
not by using the short circuit protection.

Of course, burn em if you got em... its good learning
experience.  ;^P

Example... the 78xx regulators are "short circuit
protected"... at a temperature that  makes them
miniature hotplates.  NOT recommended for long term
use... better to make an orderly shutdown if the
circuit is overloaded. The protection circuit is more
intended to perserve life while a fuse clears... not
to run for hours that way. It will die.  If you learn
from it you got your money's worth.  If you sent a
thousand into the field, you'll be sorry in the end...
  :^P

H^) harry

--- Dave Manley <dlmanley at sonic.net> wrote:

> Good point, but in this case it is just a single
> output, one that most 
> of the time is off, and when on isn't likely to be
> at max value for 
> long. This application is a one-off, on a purchased
> board.  Unless he 
> wants to dead-bug a part or break out the standoffs
> and some perf board 
> for added parts, the easies thing to do is try it
> with the layout he 
> has.  If it doesn't work, then move on to a
> different, more complicated 
> approach.  The comment was just to say to a
> beginner: "don't be afraid 
> to try some different resistor values and see what
> happens".  Playing 
> around with values is a good way for a beginner to
> get a basic feel for 
> how things work and can lead to a desire for deeper
> knowledge.  In the 
> unlikely event you burn out an opamp or a LED, it is
> just another lesson 
> learned: don't believe everything you read on the
> internet ;-)
> 
> harry bissell wrote:
> > Watch out... short circuit protection does not
> guarantee life...  
> > Overload on multiple outputs might still exceed
> > package dissipation.  If I was going to use the
> opamp ~to~ the current 
> > limit... I'd recommend a single 741
> >
> 
>